Method of percussive welding



Oct 25, 1949; I J, TRQTT 2,485,790

METHOD OF PERCUSSIVE WELDING Original Filed July 51, 1944 2 Sheets-SheetI Q vwewtoz A937 J n/Zea 4/: 75022 Oct. 25, 1949. w, J, TROTT 2,485,790

METHOD OF PERCUSSIVE WELDING Original Filed July 51, 1944 2 Sheets-Sheet2 1 5140011: win/ell J 75022 @513 2 alien c4 11 i Q WQ\\\\\\\\\ 7//4%wmPatented Oct. 25, 1949 METHOD OF PERCUSSIVE WELDING Winfield J Trott,Detroit, Mich., assignor to General Motors Corporation, Detroit, Mich.,a corporation of Delaware Original application July 31, 1944, Serial No.

547,360, now Patent No. 2,430,260, dated November 4, 1947.

Divided and this application May 18, 1946, Serial No. 670,733

1 Claim.

This invention relates to a welding method and more particularly to amethod for welding fine or thin wires to larger bodies.

This is a division of my copending application Serial No. 547,360, filedJuly 31, 1944, claiming an apparatus for percussive welding now Patent2,430,260, dated November 4, 1947.

Very frequently it occurs that it is necessary to weld or permanentlysecure one end of a small diameter wire to a larger body such as in asocket base and in some of these instances to secure such wire at thebottom of a hole or depression.

It is therefore an object of my invention to provide a method forwelding wires or thin structurally weak bodies to larger ones.

It is a further object of my invention to provide a percussive weldingmethod for securing one end of wires at the bottom of depressions.

It is a still further object of my invention to provide a method forwelding thin wires to larger bodies rapidly without damageto the wireper se.

With these and other objects in view which will become apparent as thespecification proceeds, my invention will be best understood byreference to the following specification and claim and the illustrationsin the accompanying drawings, in which:

Figure 1 is a schematic diagram illustrating the various parts of myinvention, a portion of the actual contact unit being broken away andshown in section.

Figure 2 is a vertical section taken through the actual welding portionto show the finished weld.

Figure 3 is an enlarged vertical section taken through the applicatorfixture.

Figure 4 is a sectional view taken on line 4-4 of Figure 3, and

Figure 5 is a circuit diagram showing the power supply unit for mydevice.

, Briefly, in percussive welding, a condenser of suitable size is fullycharged and then connected acrossthe work and the, part to be weldedthereto, the current fiow from the part to the body being suflicientwhen the condenser discharges to cause fusion of the members and a Weld.In my apparatus, therefore, I have provided, as shown in Figure 1, avoltage supply means 2, a condenser bank 4 and an applicator unit 6, thelatter being adapted to physically engage the part 8 to which the smallwire is to be 2 capacity of the bank depending upon the size andcharacter of the parts being welded.

In general, the power supply is connected to power lines. Condensers areconnected to the wire to be applied to the block and to the block 8,these being held in spaced relation. Knob I6 is set to proper voltagevalue and switch 20 is closed. Switch 22 is closed to charge thecondensers. A cathode ray tube is connected into the circuit later to bedescribed, the pattern of the cathode ray head showing to the operatorwhen the condensers are fully charged. The power is left on tocompensate for leakage losses in the condenser circuit. When they are inproper position, the wire being exactly over the point at which it is tobe welded, a trigger is operated to release spring means which causesthe wire to approach the spot at which it is to be welded at apredetermined rate and when it reaches the surface the condenserdischarge takes place causing fusion of the two parts to be securedtogether. The switch 22 is then turned off and the Weld is complete.

Since, however, a majority of the wires to be so secured are not ofsufficient mechanical strength to resist bending if of any length and ifthe speed at which they approach the larger body is appreciable and alsomay bounce off the surface, I have provided a special applicator or toolto properly apply these wires by the general method above mentioned.

Referring to Figure 3, there is shown therein a main cylinder body 24,the lower portion of which is externally threaded and has thereon anadjustable fiber collar 26. ,A sleeve 28 of an insulating material isapplicable over the lower end of the body 24 and up into engagement withthe collar 26. This sleeve is for spacing and also may have a specialconfiguration of the lower surface to permit proper positioning of thewhole unit on different contours. The upper end of the body 24 is alsoexternally threaded and has applied thereto a cap 60 of insulatingmaterial, this cap having a central opening 32 therein through whichprojects a long hollow tubular member '34 having a flattened head 36.This hollow tubular member extends down into the main body 24.

The central part of the body 24 is hollow and slidably mounted thereinis a member 38 which is also in turn hollow and into which the longtubular member 34 extends. The upper end of the member 38 is of reduceddiameter as at 40 and between this section and the inner wall of thebody 24 there is housed a compression spring 42, its opposite endbearing against the inner surface of cap 30. The action of this springtends to force the body 38 to the lower extremity of the body 24 orhousing, the lower end of the latter being internally tapered as at 44and. acts 3 as a stop to the downward travel of the member 38.

A small opening 46 in the lower end of the body 24 permits a hollow tube48 to project therethrough, this tube being rigidly secured to the lowerend of the body 38 by a press fit as at 50,. Within the tube 48 isslidably mounted a long chuck member 52 of proper dimension to receivethe wire to be welded. This chuck member is axially split, as shown at54, so that the ends may be forced together to grip the wire and extendsbeyond the end of tube 48, the projecting portion being of largerdiameter, as shown at 56, and provided with a bevelled surface 58 whichengages the lower end of the tube 48. The upper end of the chuck 52 isscrew threaded into the lower end of the hollow rod 34. It will thus beevident that a central small hollow hole is provided throughout theentire length of the unit so that the wire to be welded may be fed downthrough the whole unit to the gripping jaws of the chuck.

A second coiled or helical spring Gil is provided which is concentricwith the upper end of the tubular member 34 having one end bearingagainst the under surface of the head 35 and against the top of themember 38. This spring tends to eject the tube 34 upwardly which,sincethe chuck 52 is screw-threaded thereinto, will pull the chuck headupwardly against the bevelled surface 58 and tend to clamp the chuckjaws on the wire, Different internal diameter chucks may be easilysubstituted depending upon the size of the wire to be used. A transversesliding member or trigger 62 of insulating material is provided whichengages a notch 64 in the member 38 when in one position and whentransversely moved has an arcuate section 66 to disengage said memberand permit the spring 42 to force the assembly downwardly.

Since this is a percussion welder and operates by condenser discharge,it is important to have the condensers fully charged for each operationin order to maintain a proper power input to the weld. An indication ofthe charged state of these condensers is provided by connecting in thecondenser circuit a tube '18 which is an indicator type cathode ray tubewhose active or pattern portion is substantially triangular in shape andcloses up upon an increase in applied voltage.

The tuning eye is so arranged in the circuit that when a large currentflows through the resistance 65, Figure 5, to charge the condensers thisapplies a large voltage drop across resistance 65 and the tuning eye andcauses it to close. When the condensers are fully charged this currentdrops to zero and there is no voltage drop across the resistor 65 andhence the tuning eye opens up. By therefore adjusting the voltage to thetube by variable resistor 65 it may be so set as to just open for anyone installation or set up for a given series of similar welds. If adifferent set of circumstances are met then it may have to be againadjusted so that it just opens upon energization but once set, it neednot again be adjusted until different conditions arise.

In operation the wire to be welded is fed down through the unit until itprojects out beyond the jaws 56 a small amount, for example, a quarterof an inch. During this time the operator presses downwardly on the cap36 so that the jaws will be open. When in the proper position the cap 36is released and moves upward and the wire is now clamped and ready forapplication, The unit is properly positioned over the spot at which thewire is to be welded with the insulating skirt 28 in contact with thework piece and the switch 20 is closed. This applies power to a fullwave rectifier tube 68 and by now closing switch 22 the rectifier outputis applied to the condensers. By now observing tube 10 the operator candetermine when the condensers in the bank 4 have been fully chargedassuming this has been set for this type of weld. The operator must usecare at this time not to touch the exposed conductive portions of theapplicator as they are directly connected to the charged condensers, butmost of the exterior surface of the applicator is made of insulatingmaterial such as micarta or fiber. At this time the insulating crossslide 62 may be moved until the notch 66 is in alignment with the lip onthe member 38 and spring 42 then causes member 38 to rapidly descendbringing the projecting end of the wire, as illustrated at 12, intocontact with the body 8 permitting condenser discharge and fusion. Atthis time the power supply may be de-energized.

When the end of the wire '12 engages the piece to which it is to bewelded, since it only projects a small distance beyond the end of thechuck, it will not buckle and since the chuck is so designed the lattermay slide upon the surface of the wire as the wire stops and the chucktends to proceed slightly beyond its original gripping position. If itis desired to weld the Wire to the bottom of a hole, differentinsulating sleeves such as 14 may be inserted into the hole duringwelding and porcelain insulators such as 16 shown in Figure 2 may beinserted thereafter to maintain it in proper position. Therefore, allthat is necessary to prepare the apparatus is to cock the main drivespring 42 and properly position the wire and chuck in relation to thepoint at which the weld is to be made.

It will also be obvious that through the use of different diameteropenings through the chuck a variety of different sized Wires can beaccommodated and through the amount of projection of the chuck and tube48 satisfactory welds can be made at the bottom of small diameter deepholes.

I claim:

In a method of percussively welding two members together by the steps ofdischarging a storage condenser which is connected to the two members inspaced relation, the steps of causing one member to approach the otherat appreciable speed, lightly frictionally supporting one of the membersso that upon contact of the two members there will be maintained asubstantially constant engaging force between the members durin welding.

WINFIELD J, TROTT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,145,274 Pfanstiehl Jan. 31,1939 2,145,276 Pfanstiehl Jan. 31, 1939 2,279,316 Herzog Apr. 14, 19422,308,658 Jendresen Jan. 19, 1943 2,316,597 Kershaw Apr. 13, 1943

